Distribution of sprayed particles

I study some topics about spraying products on vine leaves and especially how to adapt the quantity sprayed depending on the plant vigor.
To demonstrate the efficiency of every strategy of reducing the sprayed volume, I would like to analyse pictures of leaves on which I spray fluorescent solution.
The efficiency is linked to the homogeneity of spatial distribution of the product sprayed on the leaves, so I have to quantify this homogeneity to make some objective comparisons.
Is there on ImageJ some possibilities of studying for exemple the variance of the distance between particules and if so, could somebody explain me how? Is there some other tools which could be interesting for this issue?

Many thanks in advance,

You may want to look into some of the distance transform posts throughout the forum.